System and method for E911 location privacy protection

ABSTRACT

The invention relates to a system that enables power to be selectively applied to GPS circuitry in a cellular telephone or other mobile device only when a specific user input is detected. In one embodiment, power to the GPS circuitry may be enabled only when the user strikes the keys “9-1-l.” In other embodiments, other types of GPS enablement or disablement may be employed, such as selectively decoupling the GPS antenna. In another embodiment, the user may depress a privacy bypass button, which alternately enables and disables power to the GPS circuitry. Cellular telephones or other communication devices may therefore activate GPS location service during an emergency call, or when a user wishes to allow their location to be determined, but protect the privacy of that user&#39;s location and movement at other times.

TECHNICAL FIELD

[0001] The invention relates generally to wireless communications. Morespecifically, the invention relates to mechanisms to selectively enableor disable GPS circuitry in a cellular telephone or other communicationsdevice.

BACKGROUND OF THE INVENTION

[0002] The Federal Communications Commission (FCC) has mandated that, byDecember 2002, all cellular telephone carriers must market handsetscapable of providing an emergency locator service. This emergencylocator service, known as E911, will enable personnel at the publicsafety answering point (PSAP) to pinpoint the location of a cellulartelephone user dialing 911. This FCC mandate further requires that theuser not be able to override the emergency locator service in the caseof a 911 emergency call.

[0003] This technology has raised public concern that, in addition tobeing used for emergency location, the locator service may be used bycellular carriers or by others to track the movements of cell phoneusers without their consent. There is therefore a need for a system thatcomplies with the FCC mandate for location service while providingmaximum privacy protection for cell phone users.

[0004] One technology that is commercially used to attempt to protectthe privacy of cellular telephone users is the *67 dialing featureoffered by Bell South™ and others. This feature allows a cellular userto block caller ID transmission from a cellular handset by dialing *67before placing a call. If the user dials *67 and then 911, however,caller ID transmission will not be blocked, and personnel at the PSAPwill be able to view the caller ID data.

[0005] While this technology can be used to prevent the transmission ofcaller ID data, it does not protect against the collection ortransmission of GPS location data. There is therefore a need for asystem that can be used to selectively enable and disable thetransmission of GPS location data, preserving the transmission of thatdata during true emergency calls but blocking the accidental ormalicious activation of the GPS tracking feature. Other problems exist.

SUMMARY OF THE INVENTION

[0006] The invention overcoming these and other problems in the artrelates in one regard to a system and method for selectively activatingor deactivating E911 tracking service, in an embodiment by disablingpower to GPS locator circuitry in a cellular telephone until the keysequence “9-1-1-Send” is detected. In one embodiment, the power to theGPS circuitry in a cellular handset may be activated by detection of akeypad sequence and the rotation of a physical switch to permit powerdelivery. When the handset detects the key sequence “9-1-1” it mayoutput a signal that loads the switch into a “ready” position. When theuser presses the “Send” button, the switch closes, enabling power to bedelivered to the GPS circuitry. In other embodiments, the selectivedelivery of power may be controlled by software.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a block diagram of a cellular telephone system accordingto an embodiment of the invention.

[0008]FIG. 2 is a diagram of a keypad matrix according to an embodimentof the invention.

[0009]FIG. 3 illustrates keypad logic according to an embodiment of theinvention.

[0010]FIG. 4 is a state diagram of a finite state machine for controlprocessing according to an embodiment of the invention.

[0011]FIG. 5 is a state diagram of a finite state machine for controlprocessing according to another embodiment of the invention.

[0012]FIG. 6 is a diagram of a mechanical switch mechanism according toan embodiment of the invention.

[0013]FIG. 7 is a diagram of a privacy bypass switching system accordingto an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0014]FIG. 1 illustrates a block diagram of a cellular telephone system100 in accordance with an embodiment of the invention. The cellulartelephone system 100 may include an integrated GPS receiver 110 and GPSantenna 115. The cellular telephone system 100 may further contain abaseband processor 130 that is coupled to RF/audio circuitry 120, forinstance via a serial control interface (SPI) and a synchronous serialinterface (SSI), or other connections.

[0015] The baseband processor 130 may execute software known as modemsoftware or otherwise to control the RF/audio circuitry 120 and access aradio channel. The baseband processor 130 may also interface to the GPSreceiver 110 via a Universal Asynchronous Receiver/Transmitter (UART) orother connection.

[0016] In a 911 emergency call, the modem software may request alocation fix from the GPS receiver 110 and forward the obtained locationdata to the E911 call center, Public Safety Answering Point (PSAP) orother control point using the RF/audio circuitry 120. In addition toexecuting the modem software, the baseband processor 130 may alsoexecute other software including application software, such as a Java™application, a Wireless Application Protocol (WAP) browser or others.Application software may independently request a location from the GPSreceiver 110. If the request is granted, the application may receive thelocation data from the GPS receiver 110 and transmit the location, forinstance via the UART.

[0017] In some cases, the user may wish to deny the delivery of locationdata to the application software. For this reason, the cellulartelephone system 100 may contain a GPS enabling block 140, which mayinclude a power switch. This GPS enabling block 140 may be coupled to apower bus 150 delivering DC or other power. In normal operation, the GPSenabling block 140 may be open and power to the GPS receiver 110 may bedisconnected. This ensures that the GPS receiver 110 does not sendlocation data to a local or remote application without the user'sconsent.

[0018] The cellular telephone system 100 may further contain911-detect/control circuitry 160 coupled to the GPS enabling block 140.The function of this control circuitry is to ensure that the power tothe GPS receiver 110 may be enabled when a 911 emergency call is madeand a location fix is necessary. The FCC mandate requires that the usernot be able to override the locator service when an emergency call ismade. A user-controlled switch to activate the GPS receiver is thereforenot fully compliant with the mandate, as a user could disable thelocator mechanism in the case of a E911 call. 911-detect/controlcircuitry 160 consequently automatically enables power to the GPScircuitry when an E911 call is made.

[0019] When the 911-detect/control circuitry 160 detects the keysequence “9-1-1,” it may assert a control signal 911_detect, which mayactivate the GPS enabling block 140. When the “Send” key is depressed,the GPS enabling block 140 may act to connect the power bus 150 to theGPS receiver 110. The baseband processor 130 may then send a locationrequest to the GPS receiver 110, via the UART or otherwise. The GPSreceiver 110 may obtain the location data for the cellular telephonesystem 100, and forward the data to the baseband processor 130 over theUART or other interface.

[0020] The baseband processor 130 may then communicate the location datavia the RF/audio circuitry 120 through, for instance, a base station andmobile switch (MSC) to the PSAP or other control point. Once the E911call is completed, the modem software running on the baseband processor130 may assert a reset signal. This signal may cause the GPS enablingblock 140 to disconnect power from the power bus 150, disabling power tothe GPS receiver 110, and also causing the 911-detect/control circuitry160 to return to a surveillance state.

[0021] In some cases, the user may wish to selectively allow anapplication to obtain location data not during an emergency call. In anembodiment, the cellular telephone system 100 may also contain a privacybypass switch 170 coupled to the power bus 150 and the GPS receiver 110to activate this option. When the user presses a privacy bypass key (forexample, bypass button 710 illustrated in FIG. 7), the privacy bypassswitch 170 may close. This may establish an alternate path from thepower bus 150 to the GPS receiver 110 that circumvents the GPS enablingblock 140 to enable power to drive the GPS receiver 110. The privacybypass option may allow the user to override the location avoidancemechanism, and enable the GPS circuitry at selected or all times. Withthe privacy bypass switch 170 engaged, any software application runningon the baseband processor 130 may therefore request and utilize locationdata until that selective operation is deactivated.

[0022] There are different ways to implement the 911-detect/controlblock 160 and the GPS enabling block 140. Each of these blocks may beimplemented in hardware, in software, in firmware or mechanically, or acombination of those techniques. It is possible that certain software orfirmware implementations may be less secure than mechanical guards,although those implementations may in cases cost less to install. Forexample, if a software implementation of the 911-detect/control block160 and the GPS enabling block 140 is used, it may be possible for awireless software application, such as a Java™ virus or a WAP scriptdownloaded via the wireless carrier, to activate the GPS receiver 110and determine the user's position.

[0023] For this reason, in embodiments the 911-detect/control block 160may be implemented entirely in hardware logic and the GPS enabling block140 implemented as a physical switch, such as a motorizedelectro-mechanical switch or other device. In embodiments, a keypaddetect system may therefore be used to ensure that the inputs to the911-detect/control block 160 are only asserted when a user physicallystrikes or depresses a key.

[0024] In embodiments of the invention, software or firmware may beemployed exclusively, or in combination with some mechanical orelectronic components, to selectively activate the GPS receiver 110. Inone such embodiment of the invention the GPS enabling block 140 may beimplemented as a physical switch such as a motorized electromechanicalswitch or other device, while the 911-detect/control block 160 may beimplemented in software or firmware. In another embodiment, both the GPSenabling block 140 and the 911-detect/control block 160 may beimplemented in software.

[0025] In this latter embodiment, registers may contain a Boolean orother variable, for example as “GPS_enabled” or other, to determinewhether the transmission of GPS location data is currently permitted.The control software of the 911-detect/control block 160 may set thisvariable, in this embodiment. If the collection and/or transmission ofGPS data is not allowed, the software may block this transmission bydisallowing the application to make a location request to the GPScircuitry, by disallowing the UART to transmit GPS data, or by otheraction.

[0026]FIG. 2 illustrates a diagram of a keypad matrix 200 in accordancewith an embodiment of the invention. The keypad matrix 200 contains aplurality of keys 210 a-l arranged in predetermined rows and columns.The plurality of keys 210 a-l may be arranged such that each key in theset can be uniquely identified by its corresponding row and column. Thekeypad matrix 200 may connect to a plurality of row interconnects 220a-d, each row interconnect corresponding to a row of keys in the matrix.The keypad matrix may also connect to a plurality of columninterconnects 230 a-c, each column interconnect corresponding to acolumn of keys in the matrix. Each of the row interconnects 220 a-d andeach of the column interconnects 230 a-c may be connected to a voltagepull-up.

[0027] The keypad matrix 200 may further contain a ground plate 240situated beneath the keypad. When a user strikes a key, the rowinterconnect and the column interconnect corresponding to the key may beshorted to the ground plate 240. The row interconnects 220 a-d and thecolumn interconnects 230 a-c may be connected to a keypad decoder logicblock 250, which senses key contact and determines which key has beenpressed.

[0028]FIG. 3 illustrates keypad logic 300 according to an embodiment ofthe invention. The keypad decoder logic block 250 of FIG. 2 may includea plurality of keypad logic systems 300. Each keypad logic system 300 inthe decoder logic block 250 may correspond uniquely to one key in theplurality of keys 210 a-l. The first input to the logic system,row_input 310, may be connected to the row that corresponds to thisparticular key. The second input, column_input 320, may be connected tothe column that corresponds to this particular key. The logic system 300further includes logic 330, which may be implemented as a NOR or otherlogical gate.

[0029] When the key corresponding to the logic system 300 is pressed,the row and the column corresponding to the key may be shorted toground, and the inputs 310 and 320 may be set to a logical “0.” Thelogic 330 then asserts the output signal 340. This output may then berouted to a hardware debouncer circuit 350. The hardware debouncer block350 may additionally receive a clock input 360. The hardware debouncercircuit 350 serves to eliminate spurious key strokes by verifying thatthe key is continuously pressed for a minimum amount of time.

[0030]FIG. 4 illustrates a state diagram of a control processor forcontrolling operation of the cellular telephone system 100, which mayconsist of or include a finite state machine (FSM), according to anembodiment of the invention. A FSM is one implementation of the911-detect/control block 160 of FIG. 1, which functions to assert acontrol signal 911_detect when it detects the key sequence “9-1-1.” TheFSM in this embodiment may for instance be represented or implemented asa hardware logic state machine, for instance a Moore machine. Thecontrol operation is as follows: the control processor, such as amicroprocessor, microcontroller, digital signal processor or otherdevice may begin in an initial state 400. The initial state 400 can beentered in a number of ways.

[0031] For example, this state may be entered when the cellulartelephone system 100 first powers up, when a call is ended, after akeypad entry has timed out or at other times. The modem software runningon the baseband processor 130 may detect the situations in which it isdesirable for the control processor to enter the initial state 400, andwill assert a signal switch_init that causes the device to enter theinitial state. From the initial state 400, if a “9” input is detected,the control processor may enter the 9-detect state 410. If any otherinput is detected while the control processor is in the initial state400, the control processor may remain in the initial state.

[0032] From the 9-detect state 410, if a “1” input is detected, thecontrol processor may enter the 9-1-detect state 420; if any other inputis detected, the control processor may enter the initial state 400. Fromthe 9-1-detect state 420, if a “1” input is detected, the controlprocessor may enter the 9-1-1-detect state 430 and the output 911_detectis asserted. If any other input is detected, the control processor mayenter the initial state 400. In the case of a 911 emergency call, thereset signal switch_init may be asserted when the call is ended,returning the control processor to the initial state 400.

[0033] It may be noted that the control logic described above may assertthe 911_detect signal in the case of any key sequence including the keystrokes “9-1-1.” However, by law no telephone number may begin with thenumerical sequence “9-1-1.” Furthermore, for phone numbers in which thenumerical sequence “9-1-1” is in the middle of the phone number, forexample the phone number 643-9112, or for other keypad inputs such aswireless email text which might include a “9-1-1” string, power to theGPS circuitry will not be enabled. In this example, the 911_detectsignal may be asserted after the key strokes “643-911” are detected;however, when the “2” key is detected, the control processor may returnto its initial state 400 and the 911_detect signal may be deasserted.Therefore, the control signal will not be asserted when the “Send” keyis depressed, and power to the GPS circuitry may not be enabled.

[0034] Even considering the bar on phone numbers including the numericalsequence “9-1-1,” it may be desirable to implement the 9-1-1 logicdetect circuit in an embodiment, to provide increased protection againstinadvertent enabling of the GPS circuitry. In this case the controllogic may ensure that the 911_detect signal was asserted only in thecase where the key sequence “9-1-1” was detected without any precedingkey strokes. One such embodiment is shown in FIG. 5.

[0035]FIG. 5 shows a state diagram of a control processor forcontrolling operation of the cellular telephone system 100, againconsisting of or including a finite state machine, according to anembodiment of the invention. A software-controlled FSM may be oneimplementation of the 911-detect/control block 160 of FIG. 1, whichfunctions to assert a control signal 911_detect when it detects the keysequence “9-1-1” with no preceding key strokes. The control processor inthis embodiment is similar to the state machine reflected in FIG. 4.However, while the state machine of FIG. 4 is a Moore machine, thecontrol processor illustrated in FIG. 5 may be implemented as a Mealymachine. The associated control logic also differs from that of FIG. 4in that it eliminates the 9-1-1-detect state 430 and includes an“occupied” state 530. The control processor enters the occupied state530 whenever it is determined that a call other than a 911 call is beingplaced.

[0036] The control processor begins in an initial state 500. The initialstate 500 can be entered in a number of ways. For example, this statemay be entered when the device first powers up, when a call is ended,after a keypad entry has timed out or at other times. In an embodiment,the modem software running on the baseband processor 130 may detect thesituations in which it is desirable for the control processor to enterthe initial state 500, and may assert a signal switch_init that causesthe control processor to enter the initial state. If a “9” input isdetected while the control processor is in the initial state 500, thecontrol processor may enter the 9-detect state 510. If any other inputis detected while the control processor is in the initial state 500, thecontrol processor may enter the occupied state 530.

[0037] From the 9-detect state 510, if a “1” input is detected, thecontrol processor may enter the 9-1-detect state 520; if any other inputis detected, the control processor may enter the occupied state 530.From the 9-1-detect state 520, if a “1” input is detected, the controlprocessor may enter the initial state 500 and asserts the output911_detect during the transition. If any other input is detected, thecontrol processor may enter the occupied state 530. The controlprocessor may remain in the occupied state 530 until the modem softwareor other input asserts the switch_init signal.

[0038]FIG. 6 is a diagram of a mechanical switch mechanism 600 accordingto an embodiment of the invention. The mechanical switch mechanism 600may contain an arm bar 610. When the key sequence “911” is detected, the911-detect logic 160 may output a 911_detect control signal to amechanical actuator (not shown). This mechanical actuator may beimplemented as a rotary micro-motor, linear actuator or other drivemechanism. When the mechanical actuator receives the 911_detect controlsignal, it may become motorized to bias the arm bar 610 to travel in aspecified direction 620. The arm bar 610 may travel in direction 620until it is stopped by a rigid post or other stopper 630. This stopper630 may be located under a “Send” key 640, and may be affixed to the“Send” key 640 or to the housing support structure (not shown)surrounding the “Send” key 640 or otherwise mounted.

[0039] The action of biasing the arm bar 610 such that it causes travelin direction 620 to make contact with the stopper 630 may be referred toas the load phase, and the switch mechanism 600 may be said to be loadedwhen the arm bar 610 is in contact with the stopper 630. When the armbar 610 is in contact with the stopper 630, the user may depress the“Send” key 640. This may cause the “Send” key 640 to make physicalcontact with the arm bar 610, which in turn sets in motion the arm bar610 to continue traveling in the specified direction 620 until it makescontact with a switch 650. When the arm bar 610 makes contact with theswitch 650, power to the GPS receiver 110 may be enabled. The period oftime during which the arm bar 610 is in contact with the switch 650 maybe referred to as the release phase.

[0040] The operation of the mechanical switch 600 may further include astage referred to as a restore phase. The mechanical switch 600 mayenter the restore phase when it is determined that power to the GPScircuitry will not immediately be needed. This may occur when a callother than a 911 call is being made, when a 911 call is completed, whenlocation data has successfully been obtained or otherwise.

[0041] Depending on the implementation of the invention, differentinputs may trigger the mechanical switch 600 to enter the restore phase.If the 911-detect/control block 160 is implemented using a controlprocessor operating with the control logic illustrated in FIG. 4 or thatof FIG. 5, the mechanical switch 600 may enter the restore phase whenthe modem software asserts the switch_init control signal. If911-detect/control block 160 is implemented according to control logicillustrated in FIG. 4, the mechanical switch mechanism 600 may alsoenter the restore phase when the control processor deasserts the911_detect signal.

[0042] This difference in operation is due to the fact that the911-detect/control block 160 may be implemented at least as either as aMealy machine or as a Moore machine. The Moore machine illustrated inFIG. 4 asserts the 911_detect signal when the appropriate key sequenceis detected, and does not deassert the signal until another key strokeis detected. For this reason, the GPS enabling block 140 used inconjunction with this type of control logic may be activated when the911_detect signal is asserted, and deactivated when the 911_detectsignal is deasserted. In contrast, the control processor illustrated inFIG. 5 operates as a Mealy machine and asserts the 911_detect signalonly during the transition between states. For this reason, the GPSenabling block 140 used in conjunction with this type of control logicmay be activated when the 911_detect signal is asserted, but may not bedeactivated until the modem or other software asserts the switch_initsignal.

[0043] During the restore phase, the mechanical actuator elements may bedeactivated. This may cause the arm bar 610 to move in a seconddirection 660. If the switch 600 is implemented such that the arm bar610 moves linearly, the second direction 660 may be the oppositedirection of the first direction 620. If the switch 600 is implementedsuch that the arm bar 610 moves in an arc, the first direction 620 maybe clockwise and the second direction 660 may be counterclockwise, orvice versa. During its return, the arm bar 610 may interface with thestopper 630. However, the arm bar 610 may be constructed such that it isrigid in the initial direction but compliant on the return direction.The arm bar may therefore be able to return to its original position.

[0044]FIG. 7 is a diagram of a privacy bypass switching system 700according to an embodiment of the invention. The privacy bypassswitching system 700 is one possible implementation of the privacybypass switch 170 illustrated in FIG. 1. The privacy bypass switch 700may contain a privacy bypass button 710 which may be or include anybutton, switch, or software variable such that when the privacy bypassbutton is in an “on” state, power is enabled to the GPS circuitry, andsoftware applications may request location information from the embeddedGPS receiver 110.

[0045] In the privacy bypass system 700, when the user may engage theprivacy bypass button 710, the button may make physical contact with aswitch 720 located thereunder. In one embodiment, the privacy bypassswitch 720 may be the same type of device as the 911-detect switch 650which is controlled by the logic block 160. In this case, depressing theprivacy bypass button 710 may provide a technique for closing the switch720 that is independent of the that described in conjunction with FIG.6. In another embodiment, the privacy bypass switch 720 may be aseparate switch from the 911-detect switch 650. In this case, the switch720 may be incorporated into an alternate path between the power bus andthe GPS receiver 110. This alternate path may circumnavigate the switch650. For either implementation, when the privacy bypass button 710 is inthe “on” state, power may be enabled to the GPS circuitry, and softwareapplications may request location information from the embedded GPSreceiver 110.

[0046] The foregoing description of the invention is illustrative, andmodifications in configuration and implementation will occur to personsskilled in the art. For instance, while the invention has generally beendescribed in terms of a hybrid cellular/GPS device, in embodiments otherdevices, such as two-way pagers, wireless network-enabled computers orother clients or devices may be configured with GPS protection accordingto the invention.

[0047] In another regard, while the invention has generally beendescribed as activating or controlling the collection and/ortransmission of GPS location data triggered upon an initial “9-1-1”keypad sequence, in embodiments the device may be controlled based uponother key sequences, for instance if future sequences were designatedfor emergency purposes, or otherwise. In yet another regard, while theinvention has generally been described in terms of regulating thecollection and/or transmission of GPS location data by applying orremoving electrical power to associated circuits, in embodiments otheractions may be taken to render GPS location data available orunavailable, such as by decoupling the GPS antenna when a key strokesequence is detected. The scope of the invention is accordingly intendedto be defined only by the following claims.

We claim:
 1. A method for enabling operation of GPS circuitry in amobile wireless device, comprising the steps of: detecting an input froma user comprising at least a predetermined sequence of key strokes; andsupplying power to the GPS circuitry based upon a detection of thepredetermined sequence of key strokes.
 2. The method of claim 1, whereinthe first key strokes of the predetermined sequence of key strokescomprise the key strokes “9-1-1.”
 3. The method of claim 1, wherein themobile wireless device comprises a cellular telephone.
 4. The method ofclaim 3, wherein the cellular telephone comprises an embedded GPSreceiver.
 5. A system for enabling a GPS circuitry, the systemcomprising: a first user input; a second user input; a logic block; anda physical switch; wherein the first user input and the second userinput are coupled to the logic block, and the logic block controls theoperation of the physical switch to selectively enable the GPScircuitry.
 6. The system of claim 5, wherein the logic block comprises aMealy machine.
 7. The system of claim 5, wherein the logic blockcomprises a Moore machine.
 8. The system of claim 5, wherein the logicblock comprises control software.
 9. The system of claim 8, wherein thecontrol software is stored as firmware.
 10. A system to control thetransmission of GPS data, comprising: GPS circuitry for processing GPSlocation data; a transmission device; a variable implemented insoftware; and control logic to set the variable; wherein at least one ofthe actions of: generation of GPS location data by the GPS circuitry,and transmission of the GPS data by the transmission device is enabledor disabled depending on whether the variable is set to a predeterminedvalue.
 11. A user interface system for enabling GPS circuitry in acommunications device, the user interface system comprising: a pluralityof keys coupled to communications circuitry and GPS circuitry, at leastone of the communications circuitry and the GPS circuitry being enabledby the detection of the action of the keys in a predetermined sequence.12. The user interface system of claim 11, wherein the enablement of atleast one of the communications circuitry and the GPS circuitry iscontrolled by at least one of software logic and a physical switch. 13.A switch system used to control power to GPS circuitry, the systemcomprising: a first input; a second input; an arm bar; a stopper; and aswitch; wherein the second input comprises a mechanical input, the firstinput mobilizes the arm bar to make contact with the stopper, and thesecond input mobilizes the arm bar to make contact with the switch toenable operation of the GPS circuitry.
 14. A system for enabling powerto GPS circuitry, the system comprising: a privacy bypass button; andGPS circuitry; wherein power to the GPS circuitry is enabled if theprivacy bypass button is in a predetermined on state.
 15. The system ofclaim 14, wherein the system comprises a physical switch.
 16. A methodof obtaining location data from a GPS system, the method comprising thesteps of: executing a software application; requesting, from a GPSsystem containing a physical switch, location data; receiving locationdata from the GPS system if the switch is closed; and transmitting thelocation data if received.
 17. A method of obtaining location data froma GPS system, the method comprising the steps of: executing a softwareapplication; requesting, from a GPS system containing a softwarevariable, location data; receiving the location data from the GPS systemif the software variable is set to a predetermined value; andtransmitting the location data if the location data is received.
 18. Themethod of claim 18, further comprising a step of setting the softwarevariable to a predetermined value according to user input.